To see how this works, we need to understand the principle that gravity warps space and time. Warpage of space is easier to visualize than warpage of time. Imagine that the universe is the surface of a flat billiard table. The table’s surface is a flat space, at least in two dimensions. If you roll a ball on the table it will travel in a straight line. But if the table becomes warped or dented in places, as in the illustration below, then the ball will curve.
